Structural analysis of P. falciparum KAHRP and PfEMP1 complexes with host erythrocyte spectrin suggests a model for cytoadherent knob protrusions.

Plasmodium falciparum Erythrocyte Membrane Protein 1 (PfEMP1) and Knob-associated Histidine-rich Protein (KAHRP) are directly linked to malaria pathology. PfEMP1 and KAHRP cluster on protrusions (knobs) on the P. falciparum-infected erythrocyte surface and enable pathogenic cytoadherence of infected erythrocytes to the host microvasculature, leading to restricted blood flow, oxygen deprivation and damage of tissues. Here we characterize the interactions of PfEMP1 and KAHRP with host erythrocyte spectrin using biophysical, structural and computational approaches. These interactions assist knob formation and, thus, promote cytoadherence. We show that the folded core of the PfEMP1 cytosolic domain interacts broadly with erythrocyte spectrin but shows weak, residue-specific preference for domain 17 of α spectrin, which is proximal to the erythrocyte cytoskeletal junction. In contrast, a protein sequence repeat region in KAHRP preferentially associates with domains 10-14 of ß spectrin, proximal to the spectrin-ankyrin complex. Structural models of PfEMP1 and KAHRP with spectrin combined with previous microscopy and protein interaction data suggest a model for knob architecture.

A Plasmodium falciparum PHIST protein binds the virulence factor PfEMP1 and comigrates to knobs on the host cell surface.

Uniquely among malaria parasites, Plasmodium falciparum-infected erythrocytes (iRBCs) develop membrane protrusions, known as knobs, where the parasite adhesion receptor P. falciparum erythrocyte membrane protein 1 (PfEMP1) clusters. Knob formation and the associated iRBC adherence to host endothelium are directly linked to the severity of malaria and are functional manifestations of protein export from the parasite to the iRBC. A family of exported proteins featuring Plasmodium helical interspersed subtelomeric (PHIST) domains has attracted attention, with members being implicated in host-parasite protein interactions and differentially regulated in severe disease and among parasite isolates. Here, we show that PHIST member PFE1605w binds the PfEMP1 intracellular segment directly with Kd = 5 ± 0.6 µM, comigrates with PfEMP1 during export, and locates in knobs. PHIST variants that do not locate in knobs (MAL8P1.4) or bind PfEMP1 30 times more weakly (PFI1780w) used as controls did not display the same pattern. We resolved the first crystallographic structure of a PHIST protein and derived a partial model of the PHIST-PfEMP1 interaction from nuclear magnetic resonance. We propose that PFE1605w reinforces the PfEMP1-cytoskeletal connection in knobs and discuss the possible role of PHIST proteins as interaction hubs in the parasite exportome.

Structural analysis of the G-box domain of the microcephaly protein CPAP suggests a role in centriole architecture.

Centrioles are evolutionarily conserved eukaryotic organelles composed of a protein scaffold surrounded by sets of microtubules organized with a 9-fold radial symmetry. CPAP, a centriolar protein essential for microtubule recruitment, features a C-terminal domain of unknown structure, the G-box. A missense mutation in the G-box reduces affinity for the centriolar shuttling protein STIL and causes primary microcephaly. Here, we characterize the molecular architecture of CPAP and determine the G-box structure alone and in complex with a STIL fragment. The G-box comprises a single elongated ß sheet capable of forming supramolecular assemblies. Structural and biophysical studies highlight the conserved nature of the CPAP-STIL complex. We propose that CPAP acts as a horizontal "strut" that joins the centriolar scaffold with microtubules, whereas G-box domains form perpendicular connections.

The clinimetric properties of performance-based gross motor tests used for children with developmental coordination disorder: a systematic review.

PURPOSE: Performance-based measures of gross motor skills are required for children with developmental coordination disorder to quantify motor ability and objectify change. Information related to psychometrics, clinical utility, feasibility, and client appropriateness and acceptability is needed so that clinicians and researchers are assured that they have chosen the most appropriate and robust tool. METHODS: This review identified performance-based measures of gross motor skills for this population, and the research evidence for their clinimetric properties through a systematic literature search. RESULTS: Seven measures met the inclusion criteria and were appraised for their clinimetric properties. The Movement Assessment Battery for Children and the Test for Gross Motor Development (second version) scored highest on appraisal. CONCLUSIONS: The 2 highest scoring measures are recommended in the first instance for clinicians wishing to evaluate gross motor performance in children with developmental coordination disorder. However, both measures require further testing to increase confidence in their validity for this population.

Structural variation in PWWP domains.

The PWWP domain is a ubiquitous eukaryotic protein module characterised by a region of sequence similarity of approximately 80 amino acids containing a highly conserved PWWP motif. It is frequently found in proteins associated with chromatin. We have determined the structure of a PWWP domain from the S. pombe protein SPBC215.07c using NMR spectroscopy. The structure is composed of a five stranded beta barrel followed by two alpha helices. Comparison to the recently reported structure of a homologous domain from the mammalian DNA methyltransferase Dnmt3b reveals substantial differences both in the C-terminal helical region and in the PWWP motif.